1. Field of the Invention
This invention relates to antennas for use with radio transceivers and in particular for use with mobile telephones.
2. Description of the Related Art
The design of antennas for radio transmitter/receivers (transceivers) capable of operation in more than one frequency band is constrained by the market demand continually to reduce the overall size of radio transceivers. The term "dual mode" is generally used to describe a radio transceiver capable of operation in two separate frequency bands and that description will be used herein.
An antenna for a foldable or "flip" telephone will need to be especially compact while still being capable of providing satisfactory performance. Simplified illustrations of a foldable phone are given in the accompanying figures. Foldable phones as illustrated in the figures usually comprise two housings of approximately the same size.
When such a telephone is in the closed position, performance of the antenna must also be sufficient to enable the satisfactory reception of incoming signals. The two sections of the flip phone are usually connected by a hinge mechanism and the phone is normally used in the open position as shown in figure . Incoming calls however, as well as text and data messages must be received when the phone is in the closed position with the two sections of the phone pushed together.
The display screen and keypad would usually be located in the bottom section of the phone.
The performance of many prior art antennas is significantly reduced by the proximity of the user during operation of the phone. It has been observed, however, that for antennas constructed in accordance with the invention only a small degradation occurs (less than 1 dB).